<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    手机号: <input type="number"> <button>发送</button>

    <script>
        var btn = document.querySelector('button');
        var count = 6;
        var timer;
        btn.onclick = function(){
            timer = setInterval(function(){
                // 刷新按钮里边的呢 数字
                btn.disabled = true;
                count--;
                btn.innerText = count + '秒';
                if(count===0){
                    clearInterval(timer);
                    btn.disabled = false;
                    btn.innerText = '发送';
                }
            },1000)
        }
    </script>
</body>
</html>